Method of cold-drawing refractory materials



Patented Aug. 24, 1926. v I

UNITED STATES PATENT OFF CE-9.;

WILLIAM BENJAMIN G130, M81 ORANGE, NEW JERSEY, ASSIGN BY IRENE A8- SIGNKEN'IS, .lO WESTINGHOUSE LAIIOOIPM; OOBPOBA'IIOII' OI' 2mm VAIHIA.

,Ho Drawing.

This invention relates to the art of wire drawing and particularly to the cold drawing of refractory metals.

a It has ;for one of its objects the provision 5 of a more economical and efiicieiit method of drawing such metals and is especially applicableto the cold drawing of molybdenum.

Another object of the'invention is the provision of a method for drawing said metals which will yield a product of higher tensile strength and resilience and in general ossess better qualities as a support for a lament in incandescent lamps than could be secured heretofore. A special object is the provision of a copper-coated molybdenum wire for use in incandescent lamps.

According to the best process heretofore lmown, molybdenum wire was drawn hot to about 20 mil diameter, because of the extreme difliculty of drawing it cold. However, to secure the valuable effects of cold working, it was necessary to draw the molybdenum cold from about 20 mil diameter to finished sizes. In the process ofcold drawing, the wire became so hard that, coming in contact with the die, an excessively high rate of die wear resulted. It was,-

therefore, necessary to anneal the wire frequently in order to soften it. The annealing rocess however,caused the wire to lose the esirable properties which had been given it by the cold working.

While an adherent coating of a lubricant, such as graphite, could be baked on in a hot drawing process, this could not be done with small-size wire because the temperature necessary to accom lish this would weaken such small wire su ciently to make it impractical to draw it. The small-size wire, therefore, had to be cold drawn; without a lubricant.

Another disadvantage of former processes was the gradual increase in diameter of a single piece of wire as it was drawn through the die on account of thehigh rateof die wear. The frequent breaking of the wire necessitated the use .of a single-head wire- 1 drawing machine instead of the much more eflicient multiple-head type of machine, thereb causing the efliciency of the machine and o the operator to be low.

My invention provides a process whereby a refractory metal may be worked cold to been wor union or oLn-nnawmo maacroar laa'raams.

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any extent without the necessity of annealing. Since the amount of cold working invention provides a method of controlling the degree of these properties within certain limits. It is a well-known fact that the cold worklng of the metal hardens it and gives it a higher tensile strength and greater resilience, and that the process of annealin produces opposite effects. A metal whic has ed while cold often ossesses valuable properties in' a higher egree than is possessed by the same metal when worked ot; for instance, cold workin gives a metal of greater hardness and igher tensile strength than does hot working.

This invention provides a rocess for cold 3 working refractory metals w ich heretofore have had to be worked hot because of the lack of a rocess by which they could be worked 0015.

In drawing soft metal into wire there is practlcally no wear on the dies. By coating a hard metal, such as molybdenum, with a soft metal, thus interposing a la er of soft metal between the hard molyb enum and the die, the hard metal can be drawn with the die wear of the soft metal. The soft metal acts asa lubricant for the drawing of the hard metal. The advantage in using a metal coating as a lubricant instead of graphite or greases lies in the fact that the metal provides a continuous coating, whereas other lubricants are more or less discontinuous or non-uniform so that they allow the wire to touch the die at some points.

Although soft metals have heretofore been proposed as lubricants, they seem to have proved unsatisfactory in drawing refractory metals because of the great difliculty exper1- enced in applying them to the metal to be drawn. Apparently, they could not be made to adhere to a body composed of refractory.

metal. 1

In practicing my invention, a molybdenum wire or rod is coated with copper or other soft metal which. will serve asa lubricant.

Brass, lead and other soft alloys and metals fer to copper plate the molybdenum by apl in a coatln of co per oxide, reducing thg ox ide and mglting the copper. The body of molybdenum which may be a rod, is coated by passing 1t through a mixture whlch consists of copper oxide suspended in an alcoholic solution of shellac. This mixture may consist of 100 cc. of an 18% alcoholic solution of shellac and 100 grams of 200 mesh copper oxide; the proportions may be varied to suit varying conditions, such as the amount of reduction to be made in the diameter of the rod and the thickness of the copper coating desired in the product. The coated rod is then passed through an electric furnace having a reducing atmosphere, such as hydrogen, and a temperature somewhat above the melting point of copper, the temperature depending on the rate at which the wire is passed through the furnace. The copper oxide is thereby reduced to copper and the latter. fused to the wire in a smooth coating which will adhere to the molybdenum through swaging, rolling, drawing, and other ordinary operations used in its frabrication. This method of applying the copper produces a copper coating of the desired softness. Using an additional lubricant,

I such as a soap solution, the copper coated molybdenum wire is drawn cold, which may now be done on a multiple-head wire-drawing machine, to any desired diameter without the necessity of annealing. The copper remains as a sheath on the molybdenum core to the smallest gage desired. The coppercoating may then bedissolved off or retained as desired.

If the copper-coated molybdenum is used as a support for a tungsten filament of an incandescent lamp, part of the copper is oxidized to copper oxide by a flame used during the operation of inserting the support into the button of the arbor of the lamp. This copper oxide acts as a getter or beneficial agent to improve the quality of the lamp.

By means of this invention, allowing refractory metals to be cold worked, the finished product possesses improved physical properties which could not be secured by previous processes of working, thereby makmg it more valuable for various uses, especiallyas a support for a filament of an incandescent lamp.

Another improvement in the art which this invention provides is a process by which certain physical properties of a metal may be regulated within a certain range. This is accomplished because my invention ermits anyv amount of cold working to be one on the metal, and because the amount of cold working determines the degree of certain physical properties.

The superior 'qualities possessed by wire manufactured according to the present invention allow the use of wire of smaller diameter for a given, purpose than is necessary with hot-drawn wire or with wire which has been annealed, whereby a considerable economy is effected in the use of expensive metals.

What is claimed is: 1.- The method of cold-working a re'fractory metal of the groups including molybdenum, tantalum, tungsten, chromium, zirconium, uranium, thorium and the like, which comprises coating said metal with a reducible compound of a metal which has a. lubricating property, reducing the said oxide to its metal, fusing the metallic coating and colddrawing the coated metal.

4. The method of cold-working a refractory metal of the groups including molybdenum, tantalum, tungsten, chromium, zirconium, uranium, thorium and the like, which comprises coatin said metal with a metallic oxide reducible by hydrogen, the metal of which has a lubricating roperty, reducing the said oxide to its met-a fusing the metallie coating and cold-working the coated metal.

5. The method of working molybdenum, which consists in coatin it with a continuous sheath of a metallic ubricatin material anldi working the metal-coated mo ybdenum co 6. The method of drawing molybdenum, which consists in coating a molybdenum rod with a continuous sheath of a metallic lubricating material and then cold-drawing the coated rod.

7. The process of drawing molybdenum which consists in coating said metal with a reducible oxide of a metal which has a lubricating property, reducin the said oxide to its metal, fusing the meta a coating, and cold drawing the metal-coated mol bdenum.

8. The'process of working mo ybdenum which consists in coating said metal with a metallic oxide reducible by hydrogen, the metal of which has a lubricating property, reducing the said oxide to its metal, fusing the metallic coatin and cold-drawing the metal-coated molyb enum.

9. The process of working molybdenum which consists in coating said metal with copper oxide, reducing said oxide to copper,

.an oxide of copper in t fusing the copper and cold working the copper-coated molybdenum.

10. As an article of manufacture, a body of refractory metal of the groups including molybdenum, tantalum, tungsten, chromium, zirconium, uranium, thorium and the like clad with an adherent fused coatin of copper reduced from the oxide thereof w 'Ie the latter is on said metal.

11. As an article of manufacture, a body of refractory metal of the groups including molybdenum, tantalum tungsten, chromium, zirconium, uranium, t orium and the like clad with an adherentcoating of copper sintered to said refractoryx metal by reducing e form of a coating on said refractory metal.

12. As an article of manufacture, a body of mol bdenum coated with an adherent metal fbrmed by reducing an oxide of the latter on said mol bdenum.

13. As an artic e of manufacture, a body of molybdenum clad with a coating of copper united to said molybdenum by reducing an oxide of copper thereon.

14. A resilient support for the filament of an incandescent lamp consisting of a copper-coated molybdenum wireformed by reducing an oxide'of copper on said molybdenum .wire.

15. As an article of manufacture, a composite body comprising a refractory metal terial alteration in the relative pro ortions of the coating material and the re ractory metal.

16. As an article of manufacture, a composite body comprising a refractory metal of the groups including'molybdenum, tantalum, tungsten, chromium, zirconium, uranium, thorium and the like, clad with a fused coating of copper, said clad body capable of being worked without material alteration in the relative proportions of the copper and refractory metal.

17. As an article of manufacture, a mechanically worked metallic core of a refractory metal having formed thereon by the reduction of an oxide of copper, an adherent fused coating of copper.

18. As an article of manufacture, a cold worked metal having an integral coating of copper formed thereon by reducing the oxide of copper.

In testimony whereof, I have hereunto subscribed my name this tenth day of J anuary 1921.

BENJAMIN GERO. 

